Post-Migration to new server breaks SMTP connection

This is strange. Using Windows Server/Exchange 2003, I have two instances up on two different servers. Server1 is the original server and Server2 is the new one to which I’m migrating users. I successfully moved three accounts using the same services to the new server and after a couple of minor hiccups, they work great over IMAP, Exchange and SMTP both secure and non-secure. I have a user whose mail was working fine until I moved him to the new server. Now he can’t use the SMTP service unless I add him to the domain admins group. The message from a telnet test says that he doesn’t have permission otherwise. The one major difference between this and the old server is that I disable anonymous logins. Anybody seen this?